The present invention relates to the general field of telephone communications. In more particular, the invention relates to systems to assist telephone communications by those persons who are deaf, hard of hearing, or otherwise have impaired hearing capability.
Most modern human communications in both social and business environments takes place through sound communications. Yet within modern society there are many persons who have attenuated hearing capability. To assist those persons in making use of our telephonic communication system built for the hearing majority, there has been developed a system of telephone communication which has been principally used by the deaf community. That system makes use of a category of device known variously as a telecommunication device for the deaf (TDD), text telephone (TT) or teletype (TTY). Current TDDs are electronic devices consisting of a key board and a display as well as a specific type of modem, to acoustically or directly couple to the telephone line. Modern TDDs permit the user to type characters into their keyboard, with the character strings then encoded and transmitted over the telephone line to be displayed on the display of a communicating or remote TDD device.
Most TDD communication is conducted in an idiosyncratic code specific to the community of TDD users. This code, known as Baudot, evolved historically at a time when many telecommunication devices for the deaf were based on mechanical or electromechanical devices rather than the current technology based on digital electronic components. Accordingly, the Baudot protocol was constructed for a set of constraints which are no longer relevant to present date devices. The original Baudot protocol was a unidirectional or simplex system of communication conducted at 45.5 Baud. The conventional Baudot character set was a character set consisting of 5 bit characters and the system encodes the bits of those characters in a two-tonal system based on carrier tones of 1400 and 1800 Hertz.
The system of TDD communications is widely used and in fact has become indispensable to the deaf community throughout the industrialized world. Deaf persons extensively communicate with their neighbors and with other deaf and hearing people remotely, using the TDD system. In addition, systems have been developed to facilitate the exchange of communication between the deaf community and hearing users who do not have access to or utilize a TDD device. In the United States, telephone companies have set up a service referred to as a "relay." A relay, as the term is used herein, refers to a system of voice to TDD communication in which an operator, referred to as a "call assistant," serves as a human intermediary between a hearing user and a deaf person. Normally the call assistant wears a headset that communicates by voice with the hearing user and also has access to a TDD device which can communicate to the deaf user using a TDD appropriate protocol. In normal relay operations in the prior art, the call assistant types at a TDD keyboard the words which are voiced to her by the hearing user and then voices to the hearing user the words that the call assistant sees upon the display of his or her TDD. The call assistant serves, in essence, as an interpreting intermediary between the deaf person and the hearing person to translate from voice to digital electronic forms of communication.
A limitation in the effectiveness of current relay protocols is the necessity for the call assistant simply to type what is said. Typical call assistants can usually type reasonably well, typically in the range of 30 to 50 words per minute. While systems exist which permit the digital encoding of verbal communications at a faster rate, such as court stenography used in the legal system, such systems require extensive special training and are impractical for the numerous call assistants required by the relay systems in operation today. This limitation on the speed of conversion from speech to digital communications hampers the effective flow of communication in a relay call between the hearing person and a deaf person, since most hearing people speak at a rate which is higher than most call assistants can type. In addition, since conventional Baudot communications is unidirectional, the flow of conversation in a relay assisted communication session can be somewhat awkward. For example, first the hearing person must voice a statement or question. Then the calling assistant must type that statement or question, which is then transmitted at Baudot speeds, which are slower than normal human voice communication, to the deaf person. The deaf person waits until the entire statement or question is transmitted to him or her, after which he or she composes a response and types it in at his or her TDD. Then the communication flows backward to the call assistant who must voice to the hearing person what the deaf person has typed at his or her terminal. This process enables a degree of two-way communication between a deaf person and a hearing person, but the system tries the patience of the hearing person, since it is typically not conducted at a pace anywhere close to normal human communications.